This invention generally relates to apparatus for playing a rotary recording medium in a quasi-slow-motion reproduction, and more particularly to apparatus for playing a rotary recording medium in a quasi-slow-motion reproduction, in either the forward direction or the backward direction by a use of a simple circuit construction.
Systems have been realized in which a recording system forms pits in accordance with an information signal to record the information signal along a spiral track on a flat rotary recording medium (hereinafter referred to as disc), without requiring a groove to be formed therein. A reproducing stylus traces over this track to reproduce the recorded information signal in response to variations in the electrostatic capacitance which result from the recorded pits.
In this system, since no groove is provided on the disc for guiding the reproducing stylus, pilot or reference signals are recorded on or in the vicinity of a track of the information signal, such as a video signal. Upon reproduction, the reference signals are reproduced together with the video signal. A tracking servo control is carried out so that the reproducing stylus accurately traces along the track in response to the reproduced reference signals.
In the above disc, either one of first and second reference signals fp1 and fp2 is recorded at an intermediate position between center lines of adjacent track turns. Moreover, the side on which the first and second reference signals are recorded with respect to one track turn changes over every one track turn. That is, when the first and second reference signals are respectively recorded on the right and left sides of one track turn, the relationship between the recorded positions of the reference signals is such that the second and first reference signals are respectively recorded on the right and left sides of adjacent track turns. Furthermore, a third reference signal is used as a changeover signal for telling the servo system whether is recorded for every track turn at recording changeover the first or the second reference signal is on the right or the left.
In a reproducing apparatus, a changeover operation is performed in response to the third reference signal to provide a servo tracking control signal from the reproduced first and second reference signals.
Since no grooves are provided on the above disc, the reproducing stylus can be transferred laterally from one track to another, without damaging either the reproducing stylus or the disc. Accordingly, in addition to the special reproduction such as still reproduction, slow-motion reproduction, and quick-motion reproduction, the system is capable of performing a random access in which the reproducing stylus is transferred to a desired position at high speed to reproduce the desired information.
On the other hand, due to the restriction on the relative speed between the disc and the reproducing stylus, the recording capacity of the disc, the size of the disc and the like, the discs which have been realized are standardized so that two frames, that is, four fields of video signals are recorded on each track turn of the disc. Accordingly, the disc has the vertical synchronizing signal recorded at four positions for every track turn of the disc. Furthermore, the third reference signal is recorded at one predetermined vertical synchronizing signal recorded position corresponding to the recording changeover position of the above first and second reference signals.
When a slow-motion reproduction is to be performed with respect to the above type of a disc, the reproducing stylus is kicked or shifted from one track to an adjacent track at the position where a vertical synchronizing signal is recorded, so that noise is not generated in the slow-motion reproduced picture. Therefore, in the conventional slow-motion reproduction system, the above described kicking or shifting of the reproducing stylus was performed at one or a plurality of radial positions where the four vertical synchronizing signal are recorded within one track turn. The stylus is kicked according to the slow-motion ratio and according to whether the slow-motion reproduction is in the forward direction or the backward direction.
However, in this conventional system, the vertical synchronizing signals are at positions which may vary. Therefore, the reproducing stylus is kicked or shifted according to the slow-motion ratio and the direction of the slow-motion reproduction, respectively vary. Hence, there was a disadvantage in that the circuit had to be too complex in order to form kick or shift pulses at the positions where the vertical synchronizing signals are recorded in accordance with the slow-motion ratio and the direction of the slow-motion reproduction.